Japanese Unexamined Patent Application Publication No. 2006-100801 discloses a vertical Schottky barrier diode including a low-concentration n-type GaN drift layer disposed on a low-dislocation-density GaN substrate, a Schottky electrode disposed on the drift layer, and an ohmic electrode (cathode electrode) disposed on the back surface of the n-type GaN substrate. This related-art example also discloses that use of the low-dislocation GaN substrate as a substrate in the Schottky barrier diode reduces dislocation within the drift layer composed of a low-concentration GaN layer epitaxially grown on the GaN substrate, controlling increases in backward leakage current caused by dislocation and thus improving the backward withstand voltage. This related-art example also discloses that use of the GaN substrate allows epitaxial growth of a sufficiently thick drift layer without causing degradation of crystal quality, making it easy to design the thickness and carrier concentration of a drift layer which causes no punch through and is intended for ideal breakdown.
Japanese Unexamined Patent Application Publication No. 2008-124137 discloses a vertical Schottky barrier diode that uses an n-type silicon substrate as a substrate for cost reduction and includes: a convex selectively-grown nitride semiconductor layer that is disposed on the n-type silicon substrate, composed of multiple nitride semiconductors, and has a thickness of 10 μm or more; anode electrodes in Schottky contact with the crests of the convex selectively-grown nitride semiconductor layers; cathode electrodes in ohmic contact with the back surface of the n-type silicon substrate; an insulating film for filling and flattening recesses formed on sides of the adjacent concave selectively-grown nitride semiconductor layers, and wiring lines for electrically connecting the anode electrodes formed on the convex selectively-grown nitride semiconductor layers. This related-art example also discloses that use, as a carrier layer, of the nitride semiconductor layer convexly selectively grown on the low-cost silicon substrate can suppress the effect of the difference in thermal expansion between the carrier layer and the substrate, which can grow a film having a thickness of 10 μm or more without making cracks on the convex nitride semiconductor layer and thus improve the withstand voltage of the diode.